Network Formation in Asset-Tracking System Based on Asset Class

ABSTRACT

A plurality of wireless transceivers are associated with assets and each transceiver is assigned a class designation representative of an attribute, characteristic, relation, or behavior of its respective asset. Class based network formation routines are utilized to establish hierarchical networks based on asset classes, and the asset class is used by each transceiver to screen communications intended for receipt by transceivers of the same class. The overall wireless data communication network results in reduced power consumption and signal interference in asset-tracking applications. The transceivers may include a query handling routine for forming a dynamically distributed hierarchical database system. Furthermore, a recipient transceiver selectively receives communications from other local transceivers by transmitting at incrementally stronger power levels to successive groups of transceivers, and receiving reply transmissions only from a limited number of the transceivers that excludes those transceivers from which communications already are received.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The application is: (1) a continuation-in-part of and claims the benefit under 35 U.S.C. Á§120 to U.S. patent application serial No. 09/681,282, titled CLASS SWITCHED NETWORKS FOR TRACKING ARTICLES, which was filed on Mar. 13, 2001, which is incorporated herein by reference, and which itself is a nonprovisonal of and claims the benefit under 35 U.S.C. Á§119(e) to U.S. patent application serial No. 60/257,637, titled CLASS SWITCHED NETWORKS FOR TRACKING ARTICLES, which was filed on Dec. 22, 2000, and which is incorporated herein by reference; and (2) a continuation-in-part of and claims the benefit under 35 U.S.C. Á§120 to international patent application serial No. PCT/US01/49513, titled NETWORK FORMATION IN ASSET-TRACKING SYSTEM BASED ON ASSET CLASS, which was filed on Dec. 26, 2001, which was published in English under Article 21(2) of the Patent Cooperation Treaty, which is incorporated herein by reference, and which itself is a nonprovisonal of and claims the benefit under 35 U.S.C. Á§119(e) to the filing date of U.S. patent application serial Nos. 60/257,637, titled CLASS SWITCHED NETWORKS FOR TRACKING ARTICLES, which was filed on Dec. 22, 2000, and which is incorporated herein by reference, and 60/257,398, titled STEP-POWER FILTERING FOR MULTI-CHANNEL COMMUNICATION, which was filed on Dec. 22, 2000, and which is incorporated herein by reference.

BACKGROUND OF INVENTION

[0002] The present invention relates broadly to forming ad hoc networks with radio transceivers based on common designations of the transceivers and, in particular, to forming ad hoc networks and distributed databases with radio transceivers in an asset-tracking system based on asset class designations of the transceivers.

[0003] Wireless ad hoc networks allow node-to-node communication without central control or wired infrastructure. Such networks may have dynamic, randomly-changing, multihop topologies composed of wireless data communication links between the nodes. Ad hoc networks are advantageous because they are inexpensive, fault-tolerant, and flexible. Various known methods relate to data transmission within an ad hoc wireless data communication network. However, most known methods do not address self-configuration of wireless nodes for the formation and maintenance of efficient network topology.

[0004] Known ad hoc networking methods typically organize the network on the basis of geographic proximity of the nodes or the strength of signals received by the various nodes. Known methods of ad hoc network organization also require nodes to regularly transmit network information to all other nodes in the network, which results in increased radio traffic and interference. Increased radio interference inhibits the formation and maintenance of ad hoc networks having a large number of nodes and requires nodes to transmit at a greater power, which reduces their battery life.

[0005] Short range wireless technology such as the Bluetooth(tm) radio standard promises to remove price barriers to mobile network use. By doing so, wireless devices are becoming available for applications where wired networks have been impracticable and in which prior wireless communication networks have been too expensive or inflexible. Communication between transceivers in accordance with Bluetooth standards is at a frequency of about 2.4 GHz. While Bluetooth radio technology is an ad hoc networking solution for personal data applications, it provides for only a limited number of communication channels, thereby restricting the number of Bluetooth devices that can communicate over an ad hoc network at any given time.

[0006] With regard to asset tracking, wireless data networks are known for use in warehouse management and other asset-tracking applications. However, existing wireless data network technologies are not well suited to asset tracking, which involves a large number of network nodes (e.g., hundreds or even thousands). Furthermore, existing wireless technologies are cost prohibitive, are prone to radio frequency (RF) interference, and consume a large amount of electrical power. Accordingly, wireless data networks are not commonly used in asset tracking.

[0007] It will therefore be apparent that needs exist: for an improved low cost networking technology that has the benefits of the Bluetooth price and flexibility, but that overcomes the limited networking capacity of typical Bluetooth technology; for more efficient methods of forming, organizing, and maintaining ad hoc wireless networks; and for a wireless data network technology that accommodates a large number of nodes, reduces RF interference, and consumes less power. The present invention relates to one or more of these needs.

SUMMARY OF INVENTION

[0008] Briefly described, a first aspect of the present invention relates to a method of forming a wireless data communication network among transceivers, wherein each transceiver includes a designation with a first plurality of transceivers having a first common designation and a second plurality of transceivers having a second common designation different from the first common designation.

[0009] In preferred embodiments, this method is used in an asset-tracking application to form a wireless data communication network among transceivers, wherein each transceiver includes an asset class designation with a first plurality of transceivers having a first class designation and a plurality of transceivers having a second class designation different from the first class designation. As used herein and made apparent from the following detailed description of the present invention, an “asset” is a person or thing that is desired to be tracked. For example, with respect to a person, an asset may be an employee, a team member, a law enforcement officer, or a member of the military. With respect to an article, an asset may be, for example, a good, product, package, item, vehicle, warehoused material, baggage, passenger luggage, shipping container, belonging, commodity, effect, resource, or merchandise. Similarly, as used herein and made from the following detailed description of the present invention, an “asset class” is a grouping of assets-whether the same or different-that share something in common, such as an attribute, characteristic, relation, or behavior.

[0010] The method includes the steps of: forming an ad hoc hierarchical class based network for each of the first plurality and second plurality of transceivers; and communicating to an external network from each transceiver of each ad hoc hierarchical class based network. Communication to the external network from each transceiver of each ad hoc hierarchical class based network is accomplished by establishing a communication link between each transceiver in a level of the ad hoc hierarchical class based network, other than the highest level, with a transceiver in the next higher level of the ad hoc hierarchical class based network such that transceivers pass communications upward in the ad hoc hierarchical class based network; and establishing a communication link between a transceiver in the highest level of the ad hoc hierarchical class based network and an external network access transceiver, such that communications from transceivers in the ad hoc hierarchical class based network are passed through the transceiver in the highest level of the ad hoc hierarchical class based network to the external network access transceiver.

[0011] Another aspect of the present invention relates to a method for communicating to a recipient transceiver from a plurality of transceivers, wherein the plurality of transceivers are located within the broadcast range of the recipient transceiver. The method comprising the steps of: transmitting a communication at a first power level such that only a first group of transceivers receive the broadcast, with the communication including a command causing each of the first group of transceivers not to respond to a subsequent broadcast; and subsequent thereto, transmitting a communication at a second power level greater than the first power level such that a second group of transceivers greater than and including the first group of transceivers receive the broadcast, but such that only a limited number of transceivers of the second group respond to the broadcast. The limited number of transceivers excludes the first group of transceivers.

[0012] In a feature of this aspect of the present invention, the plurality of transceivers actually exceeds the number of transceivers from which communications simultaneously can be received by the transceiver without radio frequency interference due to its channel capacity. In this case, the first group of transceivers comprises a number not greater than the number of transceivers from which communications can be received by the transceiver without radio frequency interference due to its channel capacity. The limited number of transceivers excludes the first group of transceivers and also otherwise comprises a number not greater than the number of transceivers from which communications can be received by the transceiver without radio frequency interference due to its channel capacity.

[0013] Yet another aspect of the present invention relates to a method of forming a wireless data communication network among a plurality of transceivers for tracking assets associated with the transceivers. The method includes the steps of: assigning a class designation to a population of transceivers based on a common characteristic or behavior of the assets associated with the transceivers; selecting a primary transceiver from among the population of transceivers, the remainder of the population of transceivers being secondary transceivers; and forming a class based hierarchical network among the population of transceivers. The step of forming a class based hierarchical network among the population of transceivers itself includes: broadcasting from the primary transceiver a primary availability signal including a primary class identifier representative of the class designation assigned to both the primary transceiver and the secondary transceivers; in response to the primary availability signal, transmitting from a responding one of the secondary transceivers a registration signal including a secondary transceiver identifier; storing at the primary transceiver the secondary transceiver identifier of the responding secondary transceiver, and repeating steps (ii) and (iii) for each of the secondary transceivers.

[0014] A fourth aspect of the present invention relates to the forming of a wireless data communication network among a plurality of transceivers for tracking assets associated with the transceivers. The method includes the steps of: assigning a first class designation to a first population of transceivers based on a first common characteristic or behavior of the assets associated with the first population of transceivers; assigning a second class designation to a second population of transceivers based on a second common characteristic or behavior of the assets associated with the second population of transceivers; and propagating a first and second class based hierarchical communication networks for transmitting data among the respective first and second populations of transceivers based on their respective class designations, the first hierarchical communication network including a first root primary transceiver, and the second hierarchical communication network including a second root primary transceiver.

[0015] A fifth aspect of the present invention includes the forming of a hierarchical ad hoc network for use in tracking assets, comprising the steps of: identifying a first class of the assets having a first common characteristic or behavior; identifying a second class of the assets having a second common characteristic or behavior; associating a wireless transceiver with each of the assets of the first and second classes of assets, each of the wireless transceivers including a digital processor, a memory, and a class based network formation (CBNF) routine operable on the digital processor; selecting a first class designation representative of the first class of assets and a second class designation representative of the second class of assets; storing a first class designation in the memories of each of the wireless transceivers associated with the first class of assets; storing a second class designation in the memories of each of the wireless transceivers associated with the second class of assets; and initiating the CBNF routines of the wireless transceivers to automatically propagate, in the absence of central control, a first hierarchical ad hoc network among the wireless transceivers of the first class and a second hierarchical ad hoc network among the wireless transceivers of the second class, the first hierarchical network being automatically organized so that it is logically distinct from the second hierarchical network.

[0016] A sixth aspect of the present invention relates to a portable network device adapted for attachment to one of multiple peer assets having a common characteristic or behavior. The device includes: a wireless transceiver; a digital information processor in communication with the wireless transceiver; a power source for providing electrical power to the wireless transceiver and the digital information processor; a memory unit in communication with the digital information processor, the memory unit adapted to store a class designation representative of the common characteristic or behavior; and a class based network formation (CBNF) routine operable on the digital information processor to form a network link selectively with one of multiple peer devices attached to other peer assets and including a peer designation representing the common characteristic or behavior of the peer assets, the CBNF routine being operable to send network organization messages including the class designation and to receive network organization requests from the peer devices, to thereby selectively propagate a class based hierarchical ad hoc network among the network device and the peer devices for tracking the peer assets.

[0017] A seventh aspect of the present invention relates to a dynamic distributed hierarchical database system for asset tracking. The dynamic distributed hierarchical database system includes a plurality of computer units each associated with at least one asset having a characteristic or behavior represented by a class designation. Each computer unit includes: a memory unit for storing a profile representative of the class designation; an ad hoc class based network formation routine in communication with the memory for establishing a hierarchical network with other computer units based on the class designation; and a query handling routine for interpreting and responding to database queries received from an asset-tracking application that correspond to the class designation.

BRIEF DESCRIPTION OF DRAWINGS

[0018] Further aspects, feature, benefits, and advantages of the present invention will be apparent from a detailed description of preferred embodiments thereof taken in conjunction with the following drawings, wherein similar elements are referred to with similar reference numbers, and wherein:

[0019]FIG. 1 illustrates various network components and an example arrangement in the context of a warehouse application in accordance with the present invention;

[0020]FIG. 2 is a flowchart illustrating a preferred operation of the CBNF routine operating on Wireless Reader Tags in accordance with the present invention;

[0021] FIGS. 3-11 illustrate a time sequence that depicts Wireless Reader Tags of arbitrary classes “circle” and “triangle,” transmitting a series of messages in the course of self-organizing a hierarchical network using a bottom-up propagation approach;

[0022]FIGS. 6A, 8A, 9A, 10A, and 11A illustrate the topology of the ad hoc network formed at the stages depicted in corresponding FIGS. 6, 8, 9, 10, and 11, respectively;

[0023] FIGS. 12-21A illustrate a time sequence of ad hoc network formation using a top-down propagation approach;

[0024]FIG. 22 illustrates a step-power filtering routine utilized by a Wireless Reader Tag in accordance with the present invention; and

[0025]FIGS. 23 and 24 illustrate, respectively, Tables 1 and 2 discussed below.

DETAILED DESCRIPTION

[0026] As a preliminary matter, it will readily be understood by those persons skilled in the art that the present invention is susceptible of broad utility and application in view of the following detailed description of the preferred devices and methods of the present invention. Many devices, methods, embodiments, and adaptations of the present invention other than those herein described, as well as many variations, modifications, and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the following detailed description thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention is described herein in detail in relation to preferred devices, methods and systems, it is to be understood that this disclosure is illustrative and exemplary and is made merely for purposes of providing a full and enabling disclosure of the preferred embodiments of the invention. The disclosure herein is not intended nor is to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof.

[0027] Preferred embodiments of the present invention relate to asset tracking. In particular, each asset to be tracked is tagged with a wireless transceiver (hereinafter referred to as a “Wireless Tag” or “WT”) and reading the Wireless Tag using another wireless transceiver (hereinafter referred to as a “Wireless Reader Tag” or “WRT”).

[0028] The Wireless Tag itself preferably is semi-passive, although a passive, active, or other type of Wireless Tag could be used within the scope of the present invention. The Wireless Reader Tag itself preferable is active. A passive transceiver receives and transmits primarily using inductive energy. A semi-passive transceiver receives primarily using inductive energy and transmits using internally stored energy, such as battery. An active transceiver receives and transmits using internally stored energy, such as a battery.

[0029] In the preferred embodiments, the Wireless Tags are radio-frequency transponders (“RFTs”) and the Wireless Reader Tags are low-power radio frequency (“LPRF”) devices. As used herein, the term “LPRF” refers generally to a two-way wireless radio-frequency data communication device that transmits data in packets, and is not limited to a particular signal strength or power consumption.

[0030] Each Wireless Tag includes a unique identification (hereinafter “WT ID”) stored therein that uniquely identifies the Wireless Tag in transmissions made by the Wireless Tag and, likewise, each Wireless Reader Tag includes a unique identification (hereinafter “WRT ID”) stored therein that uniquely identifies the Wireless Reader Tag in transmissions made by the Wireless Reader Tag.

[0031] The Wireless Reader Tags preferably operate in accordance with the Bluetooth(tm) standards, which is a wireless radio specification. However, it should be understood that the invention is not limited to use with Bluetooth(tm) technology, but can be used with any wireless transceiver having the capability to communicate directly with other wireless transceivers, such as wireless Ethernet transceivers, 802.11, Home RF, and others.

[0032] In accordance with the present invention, each Wireless Tag also includes, apart from its WT ID, a “class designation” representative of an attribute, characteristic, relation, or behavior of the asset (and not the Wireless Tag itself, and each Wireless Tag is said to belong to, or be a member of, a particular WT Class based on its class designation. Identification of the WT Class for which a particular Wireless Tag is designated preferably is stored on the Wireless Tag and is utilized by the Wireless Tag in screening broadcasts for determining whether to respond thereto with a transmission.

[0033] The WT Class may represent any type of identification, as desired. For instance, a particular WT Class could represent a category of an asset, such as a ball (identified by /ball); a subcategory such as a soccer ball (identified by /soccer_ball); or a subcategory of the subcategory (a sub-subcategory), such as a size 5 soccer ball (identified by /size_(—)5_soccer_ball). When the WT Class represents a subcategory or sub-category, for example, the WT Class may also represent the category or subcategory, respectively, abstracted from the subcategory or sub-category. Thus, a WT Class representing a sub-subcategory equal to /ball/soccer_ball/size_(—)5_soccer_ball also inherently identifies a subcategory (soccer_ball) and a category (ball). Alternatively, the a WT Class may be intentionally limited to identification only of the sub-subcategory (/size_(—)5_soccer_ball). If so limited, additional information inferred from this identification about the subcategory and/or category of such WT Class then may be maintained in memory on the Wireless Reader Tag (described below) or remotely in category dictionaries or category rule sets.

[0034] When a broadcast or multicast is made to the Wireless Tags (hereinafter “WT Broadcast”), each Wireless Tag is capable of identifying a specified WT Class in the WT Broadcast and replying to the WT Broadcast with its own transmission when the specified WT Class matches its WT Class. If the WT Class does not match its class designation, then the Wireless Tag does not respond to the WT Broadcast and it makes no transmission. In this regard, each Wireless Tag is a transponder that may be selectively activated. Semi-passive transceivers that are capable of being used to respond to targeted broadcasts in accordance with the present invention, and not to every broadcast received, are well known within the art and, accordingly, the specific design of such semi-passive transceivers forms no part of the present invention.

[0035] Each Wireless Reader Tag also includes a class designation, and each Wireless Reader Tag is said to belong to, or be a member of, a WRT Class. Preferably each Wireless Reader Tag is associated with at least one WT Class for reading Wireless Tags that are members thereof. In this regard, the Wireless Reader Tag communicates with (or “reads”) those Wireless Tags having a WT Class with which it is associated by making a WT Broadcast specifying the WT Class in the transmission. The identification of associated WT Classes of a Wireless Reader Tag preferably is preprogrammed into the memory of, or otherwise maintained in, the Wireless Reader Tag. Active transceivers that are capable of being used to make broadcasts that identify targeted semi-passive transceivers for response are well known within the art and, accordingly, the specific design of such active transceivers forms no part of the present invention. Preferably, however, each Wireless Reader Tag includes a digital processor and memory for storing the WRT Class thereof and associated WT Classes, the members of which are to be read by the Wireless Reader Tag.

[0036] In one aspect of the invention, a class adoption step is also utilized in which a WRT Class is adopted by a Wireless Reader Tag that is detected as being the WRT Class of a nearby Wireless Reader Tag, or that is associated with a detected WT Class of a nearby Wireless Tag. Typically, such class adoption is performed only when the adopting Wireless Reader Tag is unable to participate in the ad hoc hierarchical network formation because of a missing or corrupted class designation. Moreover, in some circumstances such a class adoption step may be useful even if the adopting Wireless Reader Tag has sufficient class designation information to support communication. For example, a

[0037] Wireless Reader Tag attached to a pallet could periodically update its class designation by detecting the WRT Classes of nearby Wireless Reader Tags and the corresponding WT Classes of nearby Wireless Tags (e.g., those attached to items placed on a pallet). Alternatively a Wireless Reader Tag can be manually programmed with a class designation by use of a handheld communicator (hereinafter “Communicator”). The Communicator is a sort of remote control device that allows a human operator to program Wireless Reader Tags and to query Wireless Tags. Preferably, the Communicator includes a LPRF device that is controlled by application software designed to facilitate manual human interaction and communication with nearby Wireless Reader Tags and Wireless Tags. In preferred embodiments, the Communicator comprises a PDA, such as those available from Handspring Inc. or Palm Corp., that is appropriately configured for use with the present invention.

[0038] In reading Wireless Tags, a Wireless Reader Tag is capable of communicating with a limited number of Wireless Tags at any given time. Accordingly, if a large number of Wireless Tags are to be read by a particular Wireless Reader Tag, the Wireless Tags are read using a step-power filtering routine in accordance with the present invention. In this regard, a Wireless Reader Tag is capable of transmitting at different power levels. By transmitting a different consecutive power levels, a Wireless Reader Tag may read a large number of Wireless Tags that otherwise would not be read due to RF interference.

[0039] With reference to FIG. 22, a Wireless Reader Tag “M” is shown spaced at different distances to Wireless Tags S1,S2,S3,S4. In accordance with the step-power filtering routine, the Wireless Reader Tag broadcasts at a first power level 10 a transmission specifying the WT Class of all of the illustrated Wireless Tags S. The broadcast is received by the closest three Wireless Tags shown within the inner circle 1010, which represents the effective transmission range of the Wireless Reader Tag at the first power level. The broadcast includes, inter alia, a command to ignore subsequent transmission specifying the same WT Class within a predetermined time period thereafter. The Wireless Tags receiving this transmission then respond appropriately and power down for the predetermined time period.

[0040] Next, the Wireless Reader Tag broadcasts at a second, stronger power level 20 a transmission specifying the same WT Class. The broadcast is received by the closest six Wireless Tags shown within the inner circle 2020, which represents the effective transmission range of the Wireless Reader Tag at the second power level. The broadcast includes, inter alia, a command to ignore subsequent transmission specifying the same WT Class within a predetermined time period thereafter. The three outermost Wireless Tags S2 receive this transmission, respond appropriately, and then power down for the predetermined time period. The innermost Wireless Tags S1 do not respond, as each has previously been instructed to ignore this subsequent transmission.

[0041] This process then repeat two more times, whereby all fifteen Wireless Tags have been read. Specifically, the Wireless Reader Tag next broadcasts at a third, stronger power level 30 a transmission specifying the same WT Class. The broadcast is received by the closest eleven Wireless Tags shown within the inner circle 3030, which represents the effective transmission range of the Wireless Reader Tag at the third power level. The broadcast includes, inter alia, a command to ignore subsequent transmission specifying the same WT Class within a predetermined time period thereafter. The five outermost Wireless Tags S3 receive this transmission, respond appropriately, and then power down for the predetermined time period. The innermost Wireless Tags S1,S2 do not respond, as each has previously been instructed to ignore this subsequent transmission.

[0042] Finally, the Wireless Reader Tag next broadcasts at a fourth, yet stronger power level 40 a transmission specifying the same WT Class. The broadcast is received by all Wireless Tags shown within the inner circle 4040, which represents the effective transmission range of the Wireless Reader Tag at the fourth power level. The broadcast includes, inter alia, a command to ignore subsequent transmission specifying the same WT Class within a predetermined time period thereafter. The four outermost Wireless Tags S4 receive this transmission, respond appropriately, and then power down for the predetermined time period. The innermost Wireless Tags S1,S2,S3 do not respond, as each has previously been instructed to ignore this subsequent transmission. In an alternative step-power filtering technique, the power level of the broadcast is included in the transmission. Then, as each Wireless Tag receives the broadcast, the power level is noted and a range thereof is used with the WT Class for prescreening of further transmissions. In this regard, only those transmissions falling within the predetermined range about the power level of the broadcast are received and processed by the particular Wireless Tags. Thereafter, a “reset” command is broadcast to all of the Wireless Tags in order to enable receipt thereafter of a broadcast at any power level, or alternatively, the power level screening is dropped after a predetermined time period.

[0043] The WRT class designations primarily are used by Wireless Reader Tag to screen each broadcast or multicast intended for receipt by a particular class of Wireless Reader Tags (hereinafter “WRT Broadcast”). Typically, a command, query, or the like (generically referred to as a message) is communicated in a transmission to members of a WRT Class in a WRT Broadcast as part of a data packet that begins with a preamble including an identification of the WRT Class intended as the target of the broadcast. Other information may also be included in the data packet for screening purposes by each Wireless Reader Tag. Wireless Reader Tags within range of the WRT Broadcast awake from a standby mode to receive the data packet, but only process the message therein with possible transmissions in response thereto when the WRT Class of the preamble matches the WRT Class of the Wireless Reader Tag (and when the other screening information, if present, also is matched). If there is no match, then the particular Wireless Reader Tag does not process the message, drops the data packet, and returns to standby mode.

[0044] A Wireless Reader Tag or a Wireless Tag also may store in memory additional information such as: sensor derived information (e.g., temperature, humidity, altitude, pressure); a priority designation to provide improved response to selected broadcasts; a privilege level (e.g., “visitor,” “employee,” “manager,” “administrator,” and “super user”); time-sensitive information (e.g., synchronization timing, real-time sensor data, and GPS data); a characteristic of the particular tagged asset (e.g., serial number, status, process step, physical location, color, size, density); and/or a behavior of the tagged asset (e.g., temperature sensitivity, light sensitivity, shelf life). A Wireless Reader Tag also may store a WRT rank in a hierarchical ad hoc network formed by the Wireless Reader Tags (e.g., “primary” or “master,” “secondary” or “slave,” “sub-primary,” “tertiary”); and/or an identification of the WT Class for which a particular Wireless Tag is designated, indexed by WT ID for the particular Wireless Tag, especially if the Wireless Tag can store only the WT ID (e.g., when the Wireless Tag is passive).

[0045] In further accordance with the present invention, each of the Wireless Reader Tags also includes a class based network formation (CBNF) routine that enables the Wireless Reader Tags to coordinate with one another in collectively forming hierarchical ad hoc networks, each network being defined by Wireless Reader Tags of a common WRT Class (hereinafter “Class Based Network”). The CBNF routine is executed upon startup of the Wireless Reader Tag, on specific command broadcast to the Wireless Reader Tag, or as otherwise needed (such as to maintain an ad hoc network). The CBNF routine is implemented in software operable on the digital processor of each Wireless Reader Tag in the preferred embodiments. Alternatively, the CBNF routine is implemented in other ways, such as hardwired logic circuitry in each of the Wireless Reader Tags. As described in detail below, each Class Based Network is a hierarchical network that provides an efficient topology for selective communication among Wireless Reader Tags of the same WRT Class.

[0046] WRT Broadcasts are made by a network interface module (hereinafter “Gateway”) that serves as a communication link between the ad hoc hierarchical networks established by the Wireless Reader Tags and an external network, such as a local area network (LAN), wide area network (WAN), or the Internet. The Gateway includes at least a network interface and an RF interface for communication with Wireless Reader Tags of the ad hoc networks. An asset-tracking application server or equivalent computer system is connected with the external network and obtains through the ad hoc networks information on the tagged assets for compilation, analysis, and/or display.

[0047] Communication between the Gateway and a Wireless Reader Tag of the highest hierarchical level in each Class Based Network may be established utilizing step-power filtering technique if a number of Class Based Networks otherwise exceeds the multiple channel communication capabilities of the Gateway. In this respect, the Gateway is enabled to selectively communicate with such Wireless Reader Tags based on physical distance from the Gateway.

[0048] Application Server communicates with nodes of ad hoc network the external network and the Gateway to obtain and compile information regarding tagged assets. In this respect, it now will be appreciated by those having ordinary skill in the art that the nodes of these Class Based Networks comprise a distributed database of information pertaining to the tagged assets. As set forth above, a Wireless Reader Tag or a Wireless Tag stores in memory not only a WRT ID or WT ID, respectively, but also may store additional information such as, for example: class designation; sensor derived information; a priority designation to provide improved response to selected broadcasts; a privilege level; time-sensitive information; a characteristic of the particular tagged asset; and/or a behavior of the tagged asset. This stored information becomes accessible by the tracking application server through the Classed Based Networks. The asset-tracking application server also can obtain the WRT ID associated with each WT ID for intelligence gathering purposes.

[0049] Turning now to FIG. 1, a preferred embodiment of the present invention is illustrated in a shipping environment 100 including a warehouse 104. A Wireless Reader Tag 110 (also represented by “LPRF” in the drawings) is attached to each pallet 120 in the shipping environment 100. An actual implementation would involve thousands of pallets and LPRFs; however, for clarity only three pallets 120 and Wireless Reader Tags 110 are shown in FIG. 1. Assets 134 on the pallets 120 each are tagged with a Wireless Tag 130 (also represented by “RFT” in the drawings).

[0050] Each Wireless Reader Tag 110 preferably is active, while each Wireless Tag 130 preferably is semi-passive. As set forth above, passive Wireless Tags 110 and Wireless Reader Tags 130 are devices that collect RF energy inductively and selectively respond, including sending information that is stored thereon. These type of devices may be viewed as selective reflectors of incident RF signals. Semi-passive and semi-active Wireless Tags 110 and Wireless Reader Tags 130 are devices that use internal energy, in the form of a battery, to power some portion of the circuit to either detect a transmission or make a transmission. Active Wireless Tags 110 and Wireless Reader Tags 130 are devices that use internal power, in the form of a battery, to both detect and make transmissions.

[0051] Preferably, both Wireless Tags 130 and Wireless Reader Tag 110 are read-write devices, but the Wireless Tags 130 may be read-only (generally characteristic of passive devices) within the scope of the present invention.

[0052] A Gateway 140 (also represented by “NIM” in the drawings) represents a communication link between an external network (LAN) 150 and Class Based Networks formed by the Wireless Reader Tags 110. The Gateway 140 is an external network access transceiver that comprises a radio base station directly or indirectly connected to a wired network (e.g., using Ethernet, or wireless Ethernet). The radio base station portion of Gateway 140 is an LPRF-compatible module that communicates with Wireless Reader Tags 110 of the Class Based Networks. In essence, the Gateway 140 links the Class Based Network of the present invention with conventional network topologies that use conventional network protocols. The Gateway 140 thereby facilitates monitoring, controlling, and querying Wireless Reader Tags 110 and Wireless Tags 130 in the Class Based Networks using application software running on a server computer 160 connected to the external network 150. The server 160 may be operated on a general purpose computer, such as a personal computer, minicomputer, or mainframe.

[0053] A system in accordance with the present invention may include components in addition to those described above. For example, a Communicator 170 (also represented by “HIM” in the drawings) and a mobile locating Gateway 180 (also represented by “MLG” in the drawings) are provided in the preferred embodiment of FIG. 1. Communicator 170 is used to manually read class designations from network entities, such as Wireless Reader Tag 110 and Wireless Tags 130, and to assign class designations. Gateway 180, which is installed in shipping vehicle 184, has the core capabilities of a Wireless Reader Tag and a Gateway, plus at least two additional features. Gateway 180 includes a GPS receiver (not depicted) for determining geographic location of shipping vehicle 184 and a mobile interface such as a cellular or satellite transmitter 186 for transmitting data to server computer 160 via a mobile phone network 188. In implementation, the Communicator 170 and Gateway 140,180 each include a Wireless Reader Tag incorporated therein. Thus, because Gateway 140,180 and Communicator 170 each includes the core hardware and software of a Wireless Reader Tag, each can actively participate in the formation, control, and maintenance of the Class Based Networks.

[0054] The operation of the CBNF routine of multiple Wireless Reader Tags in accordance with the present invention for forming Class Based Networks now is described.

[0055] Network Formation

[0056] In accordance with the present invention, the CBNF routines of multiple Wireless Reader Tags cooperate to propagate a distinct hierarchical network among each of multiple WRT Classes of the Wireless Reader Tags. To accomplish this class based network formation, the WRT Class for each Wireless Reader Tag is stored in memory and included in the preamble of each network formation communication generated by the Wireless Reader Tag. The WRT Class may be identified by any series of codes or characters, the interpretation of which should be standardized and used by all possible recipients of network formation communications (including all Wireless Reader Tags 110, Gateways 140,180, and Communicator 170). For example, a WRT Class may include a category/subcategory list such as “/Wal-Mart/Shipment_(—)123”, or a linked list representing relationships of various categories and subcategories defined in a profile of the Wireless Reader Tag. Moreover, in this example, the WT Classes of Wireless Tags associated with a Wireless Reader Tag of the WRT Class “/Wal-Mart/Store_(—)290/Shipment_(—)123” could include “/Televisions/32in” and “/Televisions/27in”, representing 32 inch televisions and televisions 27 inch televisions on a pallet (to which the Wireless Reader Tag is attached) that is scheduled for inclusion with shipment number 123 to Wal-Mart store number 290.

[0057] Alternatively, if Wireless Reader Tags 110 are not preprogrammed in non-volatile read/write memory with a WRT Class designation, a Wireless Reader Tag 110 may acquire a class designation by reading Wireless Reader Tags 110 or Wireless Tags 130 nearest to it, and then store the class designation and other profile information in non-volatile read/write memory. Thus, when a pallet 120 is moved onto shipping vehicle 184, the pallet's Wireless Reader Tag 110 migrates to join a Class Based Network headed by Gateway 180. Gateway 180 is then able to report the migration to server 160 via a network link that it has formed with Gateway 140.

[0058] In accordance with the present invention, the CBNF routines of multiple Wireless Reader Tags cooperate to propagate a distinct hierarchical network among each of multiple WRT Classes of the Wireless Reader Tags. To accomplish this class based network formation, the WRT Class for each Wireless Reader Tag is stored in memory and included in the preamble of each network formation communication generated by the Wireless Reader Tag. The WRT Class may be identified by any series of codes or characters, the interpretation of which should be standardized and used by all possible recipients of network formation communications (including all Wireless Reader Tags 110, Gateways 140,180, and Communicator 170). For example, a WRT Class may include a category/subcategory list such as “/Wal-Mart/Shipment_(—)123”, or a linked list representing relationships of various categories and subcategories defined in a profile of the Wireless Reader Tag. Moreover, in this example, the WT Classes of Wireless Tags associated with a Wireless Reader Tag of the WRT Class “/WalMart/Store_(—)290/Shipment_(—)123” could include “/Televisions/32in” and “/Televisions/27in”, representing 32 inch televisions and televisions 27 inch televisions on a pallet (to which the Wireless Reader Tag is attached) that is scheduled for inclusion with shipment number 123 to Wal-Mart store number 290.

[0059] Alternatively, if Wireless Reader Tags 110 are not preprogrammed in non-volatile read/write memory with a WRT Class designation, a Wireless Reader Tag 110 may acquire a class designation by reading Wireless Reader Tags 110 or Wireless Tags 130 nearest to it, and then store the class designation and other profile information in non-volatile read/write memory. Specifically, a WRT can acquire or “adopt” a class designation from a surrounding WRT or WT when that function is provided for in the “profile” of the WRT. As used herein, a “profile” of a WRT includes a list of attributes that invoke operating system functions, and can include information such as “adopted class.” If, for example, a WRT that is in a manufacturing area moves past a physical boundary that puts it within a shipping area, then the WRT automatically adopts a shipping class for its previous manufacturing class. The class designations may look like this:

[0060] When in Manufacturing: /Sony/TV/24″/Manufacturing-Finishing/Serial #10

[0061] When in Shipping: /Sony/TV/24″/Shipping/Serial #10

[0062] The value to this system is that as products are completed, the class on a pallet will not need to be manually changed because it automatically updates according to location (i.e., near the shipping docks). The same may happen once a driver leaves the parking lot and the radios no longer communicate to a NIM, but now communicate with a MLG. In this case, the class designations may look like this:

[0063] /Sony/TV/24″/lntransit/ABC Trucking/Serial #10

[0064] Thus, when a pallet 120 is moved onto shipping vehicle 184, the pallet's Wireless Reader Tag 110 migrates to join a Class Based Network headed by Gateway 180. Gateway 180 then is able to report the migration to application server 160 via a network link that it has formed with Gateway 140.

[0065] The WRT Class may also include other information concerning a status, characteristic, or privilege of the Wireless Reader Tag, the network, or other conditions. Virtually any profile information can be included in the preamble and combined with class designation information to be used for network formation. Furthermore, the preamble information can be represented in any convenient format, including various encoding schemes. In one embodiment, a Walsh code is assigned to each class definition and provided to Wireless Reader Tags of the class.

[0066] Walsh codes are well understood in the field of digital wireless communications and, therefore, require only a brief explanation here. Walsh codes are used to encode data packets and to designate the class of Wireless Reader Tags that are enabled to receive and decode a particular packet of data. The association of Walsh codes with class designation information facilitates reduced battery consumption in Wireless Reader Tags by utilizing targeting methods requiring very little processing power. The use of Walsh codes also improves data security by encoding of such communications. Those skilled in the art will recognize that many other methods may be used for encoding class designation information in the preamble of data packets to facilitate class based network formation and network formation communications while reducing battery consumption and RF interference.

[0067]FIG. 2 is a flowchart illustrating a preferred operation of the CBNF routine in accordance with the present invention to form a Class Based Network. With reference to FIG. 2, upon power up, a first Wireless Reader Tag of a predetermined WRT Class initially listens (Step 210) for transmissions of other Wireless Reader Tags of the same WRT Class, which would indicate the presence of a Class Based Network for such WRT Class. If such a Class Based Network is detected, then the first Wireless Reader Tag attempts to join (Step 220) the Class Based Network as a “secondary” unit by issuing a registration request signal. Otherwise, if no Class Based Network is detected, then the first Wireless Reader Tag attempts join the overall network by establishing such a Class Based Network as a “primary” unit. This is done by transmitting (Step 230) a “primary_ready” signal to all other Wireless Reader Tags of the same WRT Class within the broadcast range of the first Wireless Reader Tag. The first Wireless Reader Tag then listens (Step 240) for replies from other Wireless Reader Tags attempting to register as secondary units in the new Class Based Network.

[0068] If no reply for registration as a secondary unit is detected, and if the WRT Class of the first Wireless Reader Tag can be abstracted, then the WRT Class is abstracted (Step 250) by truncating the class designation. For example, if the initial WRT Class is “/WalMart/Store_(—)290/Shipment_(—)123”, then the class designation is abstracted to “Wal-Mart/Store_(—)290”. The process then repeats starting at Step 210 for this abstracted class designation as the new WRT Class for the first Wireless Reader Tag. If this process continues to repeat, the class designation will not be able to be abstracted further without otherwise being generic to all classes of Wireless Reader Tags, i.e., WRT Class being “/”. At this point, the first Wireless Reader Tag attempts to connect (Step 294) to a Gateway (“NIM” in FIG. 2) and register as a member of the WRT Class that is the highest abstraction possible without being generic to all Wireless Reader Tags (i.e., as a member of the root class “/Wal-Mart”). Upon successful registration with the Gateway, the first Wireless Reader Tag then enters (Step 296) sleep-or sleep or standby-mode to conserve battery power.

[0069] If a reply from a secondary unit is detected, then the first Wireless Reader Tag registers (Step 260) the secondary unit and repeats the registration for each reply from other secondary units until a determination is made (Step 270) or until no more such replies are detected. A “cluster” in this context comprises a primary unit and the secondary units with which the primary communicates directly, and may be limited in number of units by the number of communication channels that can be supported by the primary unit operating as a cluster head. Once a cluster is full, the first unit (cluster head) responds to the next secondary unit attempting to register by promoting (Step 280) it to the status of a primary unit. The first Wireless Reader Tag-now the cluster head of the full cluster-then attempts to register (Step 290) with the newly promoted primary unit as one of its secondary units. The new primary unit, in turn, then is available to serve as a cluster head for other Wireless Reader Tags, to promote other Wireless Reader Tags to higher level primary units, and so forth, thereby propagating a hierarchical Class Based Network from the “bottom-up.” The first Wireless Reader Tag and the other Wireless Reader Tags form the Class Based Network using the same CBNF routine.

[0070] Returning to Step 270, if the cluster of the first Wireless Reader Tag does not completely fill, if no more first Wireless Reader Tags attempt to register as secondary units, and if the first Wireless Reader Tag has a class designation that is other than its root class, then the first Wireless Reader Tags abstracts its WRT Class (Step 250) by truncating the class designation and starts over the entire CBNF routine beginning at Step 210 (i.e., listening for the presence of Wireless Reader Tags of the truncated class at Step 210, etc.). Note that in accordance with preferred embodiments of the present invention, a Wireless Tag or Wireless Reader Tag will respond if its class is identified in a communication, even if the class in the communication is abstracted. Thus, a Wireless Tag or a Wireless Reader Tag having a class designation of “/sony/tv/color/24” will respond to a communication identifying the class as “/sony/tv” as its class (i.e., its abstracted class) is identified in the communication.

[0071] If no other Wireless Reader Tags are attempting to register and if the first Wireless Reader Tag's WRT Class cannot be abstracted, then the first Wireless Reader Tag attempts to register (Step 294) with the Gateway and, thereafter, enters (Step 296) into an idle mode. Alternatively, the first Wireless Reader Tag may start attempting to register with the Gateway soon after it becomes a primary at Step 230 or concurrently with filling its cluster at Step 270. Furthermore, when promoting a Wireless Reader Tag to a primary unit, the first Wireless Reader Tag would also pass to the promoted Wireless Reader Tag the responsibility for connecting with the Gateway on behalf of the cluster, possible.

[0072] In accordance with the Bluetooth standard, the Gateway will be able to communicate with seven other WRTs simultaneously. However, the targeted WRT Class can revolve on each channel as a function of time in order to address multiple WRT Classes on the single channel. Upon registration with the Gateway, the system may establish a revolving communication schedule with revolving class addressing that allows the Gateway to communicate with hundreds or thousands of WRT Classes on the channel. Synchronization between the Gateway and Wireless Reader Tags is important for proper operation of revolving class addressing and to minimize battery consumption. Accordingly, as WRT Classes are added to the overall network and establish communication with a Gateway, the Gateway may synchronize, reconfigure, and optimize the WRT Class' schedule for revolving class addressing.

[0073] The Class Based Networks also are reconfigurable in response to changes in the location, status, behavior, characteristics or class designation associated with the Wireless Reader Tags. For example, assets of a class (e.g., in-production) can be selectively transferred to a new class (e.g., shipping) by merely changing the WRT Class designation with which the assets are associated. Class Based Networks also facilitate the use of asset-tracking applications and process flow controls to track and manage the assets based on real-world requirements, such as manufacturing requirements, shipment, warehouse management, zone control, environmental impacts, etc. Class Based Networks also facilitate automated segregation and delivery of assets.

[0074] In a “top-down” CBNF routine, illustrated in FIGS. 12-21, when a cluster is filled the secondary units that have already registered with the first Wireless Reader Tag (the cluster head) may be promoted to assume the role of middle-hierarchy primary units, called “sub-primaries.” Sub-primaries, which continue as secondary units below the first Wireless Reader Tag (cluster head), then provide connectivity for any additional Wireless Reader Tags that are attempting to join the Class Based Network in clusters headed by the sub-primaries.

[0075] In both the top-down and bottom-up methods, secondary units promoted by the first Wireless Reader Tag become new cluster heads that, themselves, may provide connectivity to Wireless Reader Tags of the same WRT Class that are beyond the actual transmission range of the first Wireless Reader Tag. The Wireless Reader Tags thereby collectively form a hierarchical, multi-tiered network based on class designation that propagates both in quantity of nodes and geographic coverage. Tightly grouped Class Based Networks formed in accordance with the present invention thus make it possible to communicate to and among a particular target class of Wireless Reader Tags without requiring messages to be received, processed, or routed by Wireless Reader Tags that are not members of the target WRT Class or an abstracted Class thereof. This hierarchical Class Based Networks is an efficient topology for communicating among Wireless Reader Tags of the same WRT Class, because it reduces the number of network nodes through which messages must pass and, consequently, thereby significantly reduces RF interference and battery power consumption otherwise experienced.

[0076] FIGS. 3-11 depict Wireless Reader Tags in a time-sequence of events showing a bottom-up method of the CBNF routine. With reference to FIGS. 3-11, Wireless Reader Tags 1-6 and Wireless Reader Tags A-G are members of WRT Classes “circle” and “triangle,” respectively, which are arbitrary class designations assigned for purposes of illustration only. In this example, the Wireless Reader Tags 1-6 and Wireless Reader Tags A-G operate on up to three communication channels and one general channel (also called the control channel). The Wireless Reader Tags all include CBNF routines operating in accordance with the method shown in FIG. 2.

[0077] The CBNF routine of each Wireless Reader Tags 1-6 and Wireless Reader Tags A-G is configured to initially listen for a communication having a data packet with a preamble that identifies a Wireless Reader Tag of the same WRT Class as the Wireless Reader Tag executing the CBNF routine (see FIG. 2, Step 210). In this example, the preamble of each packet is represented by a colon-separated string of information, as follows:

[0078] :Target Class: My Profile: Action Requested: Target Cluster Head ID

[0079] where “Target Class” is the WRT Class of Wireless Reader Tags directed to wake up from standby to receive and process the data packet. In this example, the Target Class is either “/circle” or “/triangle” (there are no subcategories in this example). However, in a more complex embodiment (not shown) the Target Class designation could include subcategory information in a slash-separated list, in a linked list, with Walsh codes, or by any other method of representing category and subcategory information. The “My Profile” section of the preamble identifies the Wireless Reader Tag transmitting the communication by WRT Class and WRT ID unique to the Wireless Reader Tag. The “Action Requested” includes the message, and the “Target Cluster Head ID” identifies the Wireless Reader Tag of the cluster head or proposed cluster head, if any.

[0080] Thus, for example, with reference to FIG. 3, after listening for data packets of its WRT Class (i.e., /circle) and detecting none, Wireless Reader Tag 1 attempts to start a Class Based Network for the WRT Class of “/circle” as a primary unit by transmitting a data packet having the following preamble:

[0081] :/circle:/circle/unit1:primary_ready: no_primary

[0082] The class designation “/circle” causes only Wireless Reader Tags of the WRT Class “/circle” to receive and process the message of the data packet. Wireless Reader Tag 1, if it receives no replies, may retransmit the communication multiple times before timing out and beginning a beacon procedure or entering a battery-saving lost mode. Furthermore, the data packets (and others described below) may encapsulate a data payload or may have a null payload.

[0083] Wireless Reader Tags are preferably synchronized to allow scheduled communication to a particular WRT Class at regular intervals. When an Wireless Reader Tag communicates to a target WRT Class, the Wireless Reader Tag transmits a data packet at a time precisely synchronized with the targeted WRT Class. To conserve battery power, the receiving members of the WRT Class only power up to listen at each such interval and only for very small periods of time (e.g., a few milliseconds) when data packet for such WRT Class would normally be transmitted. The intervals at which a Wireless Reader Tag listens for communications directed to its WRT Class is called the duty cycle, which can be dynamically adjusted to respond to network communication demands while minimizing battery consumption. Depending upon the time sensitive nature of the assets being tracked and their priority, a period of inactivity may prompt a Wireless Reader Tag to limit its duty cycle to intervals of minutes or hours. After a prolonged period of inactivity, a Wireless Reader Tag may ping (transmit) to determine whether other Wireless Reader Tags are still alive and available for communication. Assuming that no network changes have occurred, the Wireless Reader Tag goes back to sleep until the next duty cycle. Network changes may cause all or a part of a Class Based Network to reconfigure.

[0084] With reference to FIG. 4, in response to the “primary_ready” signal, Wireless Reader Tags of WRT Class “/circle” within range of Wireless Reader Tag 1 respond with a registration request signal, as listed in Table 1 of FIG. 23.

[0085] Because the registration request packets include in their preambles a target WRT Class of Wireless Reader Tag 1, only Wireless Reader Tag 1 will wake up from standby to receive and process the registration request packets. The transmitters of Wireless Reader Tags 2-6 would preferably include conventional collision avoidance routines to avoid interfering transmissions of the registration request packets, as set forth by the Bluetooth specifications.

[0086] With reference to FIG. 5, in response to receipt at Wireless Reader Tag 1 of the registration_request signals from Wireless Reader Tags 2-6, the CBNF routine of Wireless Reader Tag 1 registers and acknowledges the secondary Wireless Reader Tags to form a cluster. In this example, Wireless Reader Tag 1 has a maximum cluster capacity of three secondary units. Consequently, it only registers and acknowledges the three Wireless Reader Tags from which the strongest registration request signals are received which, in this example, are Wireless Reader Tags 2-4. (Note that the ability of a LPRF device to determine signal strength is conventional and, therefore, is not described in detail herein.) By registering and acknowledging secondary units on the basis of signal strength, rather than on a first-come-first-served basis or some other basis, the CBNF routine establishes a cluster that is energy efficient for communication within the cluster. To acknowledge registration of the secondary units, Wireless Reader Tag 1 transmits an acknowledgement signal to the Wireless Reader Tags 2-4, as set forth in Table 2 of FIG. 24.

[0087] The network topology is now shown in FIGS. 6 and the cluster hierarchy is depicted in FIG. 6A. The two concentric circles of Wireless Reader Tag 1 indicate that it is a cluster head at Level 2 in the network hierarchy.

[0088] With reference to FIG. 7, with its cluster capacity now exceeded, Wireless Reader Tag 1 (the cluster head) selects from the other Wireless Reader Tags attempting to register the unit having the strongest registration request signal (in this example Wireless Reader Tag 5) and directs such unit to become a new primary unit. The new primary unit then serves as a new cluster head for a cluster in which Wireless Reader Tag 1 becomes a secondary unit (thus the “bottom-up” description of the method). In this example, the command from Wireless Reader Tag 1 to Wireless Reader Tag 5 is:

[0089] :/circle/unit5 :/circle/unit1:promote_and_request_primary: no_primary

[0090] With reference to FIG. 8, Wireless Reader Tag 5 acknowledges the promotion signal from Wireless Reader Tag 1 and begins to propagate the Class Based Network at the next higher level in the hierarchy, which now has three levels as depicted in FIG. 8A. In acknowledging its promotion and registration as a primary to Wireless Reader Tag 1, Wireless Reader Tag 5 transmits its acknowledgement packet to all units of its class within range, by the following preamble:

[0091] :/circle: /circle/unit5:primary_acknowledged: /circle/unit5

[0092] By transmitting to all units of its WRT Class within range, Wireless Reader Tag 5 efficiently registers with Wireless Reader Tag 1 and concurrently shares primary status information with all Wireless Reader Tags of its WRT Class within its broadcast range (which is different from the broadcast range of Wireless Reader Tag 1). The three concentric circles around Wireless Reader Tag 5 indicate that it is a primary in the third-level of the hierarchy of the Class Based Network.

[0093] With reference to FIGS. 9 and 9A, Wireless Reader Tag 6, upon receiving Wireless Reader Tag 5's registration acknowledgement (FIG. 8), requests to register as a secondary unit to Wireless Reader Tag 5 by sending a packet with the following preamble:

[0094] : /circle/unit5: /circle/unit6: request_primary: /circle/unit5

[0095] To which, unit 5 responds with:

[0096] :/circle/unit6: /circle/unit5: registration_ackn: /circle/unit5

[0097] This exchange results in the hierarchy shown in FIG. 9A.

[0098] With reference to FIG. 10, a Class Based Network for the WRT Class “/triangle” is similarly formed by Wireless Reader Tags A-G concurrently with the steps shown in FIGS. 3-9, whereby two distinct hierarchal Class Based Networks result as shown in FIG. 10A.

[0099] With reference to FIG. 11, if a Gateway is available, the highest level primary units (Wireless Reader Tags 5 and A in this example) register with the Gateway to establish connectivity to an external network including an application server (no shown) communicating therewith.

[0100] FIGS. 12-21 illustrate another preferred top-down CBNF routine in which the Wireless Reader Tags transmit a series of network formation communications in the course of self-organizing a hierarchical network, the topology of which is shown at various stages adjacent to FIGS. 13, 16, 19, and 21 in respective FIGS. 13A, 16A, 19A, and 21A. As with FIGS. 3-11, the transmitting Wireless Reader Tags are shown in heavy bold outline, but the hierarchical levels are not indicated this time by inner circles and triangles.

[0101] With reference to FIG. 12, a first Wireless Reader Tag 1 wakes up and reads profile information stored in its memory, including a predefined class designation of “/circle” as its WRT Class. This profile is stored into the memory of the Wireless Reader Tag 1 during an initialization of the Wireless Reader Tag 1. Based on this class designation, Wireless Reader Tag 1 then listens for transmission activity by other Wireless Reader Tags of the same WRT Class. If the nearby Wireless Reader Tags of the WRT Class have already formed a Class Based Network for “/circle” accordance with the present invention, then Wireless Reader Tag 1 attempts to join such Class Based Network. Otherwise, Wireless Reader Tag 1 attempts to organize a Class Based Network for such WRT Class.

[0102] To begin organizing Class Based Network, Wireless Reader Tag 1 transmits a primary_ready signal including its designated WRT Class. As in the CBNF routine described above in FIGS. 3-11 A, the primary_ready signal is preferably a data packet that includes in its preamble data representative of the “circle” class designation. In FIG. 12, the bold boundary of Wireless Reader Tag 1 indicates that it transmits rather than receives. The range of the transmission is depicted by dashed circle “R.” Nearby Wireless Reader Tags 2-5 and B, C, D, and E, which are within range of the primary_ready signal, each processes only the preamble portion of the primary_ready signal to determine whether the transmission if from a Wireless Reader Tag of the same WRT Class. By first processing only the preamble portion of the primary_ready signal, battery power is conserved in triangle Wireless Reader Tags B, C, D, and E. If it is of the same class, then the receiving Wireless Reader Tag-in this example, each of Wireless Reader Tags 2-5-wakes up, receives, and processes the entire primary_ready signal, and then responds as shown in FIG. 13 and described below.

[0103] With reference to FIG. 13, each of the Wireless Reader Tags of the WRT Class “/circle” that received the primary_ready signal in FIG. 12 (i.e., units 2-5) responds to the primary_ready signal with a registration_request signal. Upon receipt of the registration_request signal, Wireless Reader Tag 1 assumes the status of a primary unit, while Wireless Reader Tags 2-5 assume the status of secondary units. FIG. 13A shows the resulting 2-tiered network hierarchy tree representative of the Class Based Network thus formed between Wireless Reader Tags 1-5.

[0104] Next, with reference to FIG. 14, a third tier of the hierarchical network is formed by Wireless Reader Tag 6. In this regard, Wireless Reader Tag 6 was out of range of Wireless Reader Tag 1's primary_ready signal shown in FIG. 12, but is within range of the registration_request of Wireless Reader Tags 3 and 5 shown in FIG. 13. Wireless Reader Tag 6, which was listening during the step shown in FIG. 13, received the registration request signals of Wireless Reader Tags 3 and 5 because those signals included the “/circle” class designation matching the “/circle” class designation of Wireless Reader Tag 6. The registration request signals indicate to Wireless Reader Tag 6 the presence of a nearby Class Based Network of corresponding WRT Class, which causes Wireless Reader Tag 6 to transmit a request to join this Class Based Network.

[0105] Concurrently with the ongoing formation of the “/circle” class network, FIG. 14 also depicts the beginning stages of the formation of a Class Based Network for the WRT Class of “/triangle” by Wireless Reader Tags A-G. In this regard, Triangle Wireless Reader Tag A wakes up and listens for the presence of a “/triangle” class network. Detecting no other “/triangle” WRT Class signals, Wireless Reader Tag A transmits a primary_ready signal, similar to the transmission of Wireless Reader Tag 1 shown in FIG. 1, but with a “/triangle” class designation forming part of the preamble of the primary_ready signal.

[0106] With reference to FIG. 15, triangle class Wireless Reader Tags B, C, and D receive the primary_ready signal of Wireless Reader Tag A and respond with registration_request signals, thereby forming a second hierarchal Class Based Network, as shown in FIG. 16A.

[0107] Also shown in FIG. 15, circle Wireless Reader Tags 3 and 5 respond to the request to join of Wireless Reader Tag 6 of FIG. 14 with primary_ready signals. Wireless Reader Tag 6 then responds to the strongest primary_ready signal received (in this example, the signal from Wireless Reader Tag 5), with a registration_request. Wireless Reader Tag 6 thereby forms a third tier of the Class Based Network for “/circle” WRT Class, also as shown in FIG. 16A.

[0108] With reference to FIGS. 17-19, Wireless Reader Tags E, F, and G of the WRT Class “/triangle” each joins the Class Based Network for triangles formed by Wireless Reader Tags A, B, C, and D.

[0109] FIGS. 20-21A illustrate the completion of the Class Based Networks with the registration with the Gateway of the highest primary unit in each Class Based Network hierarchy.

[0110] As will now be apparent to one having ordinary skill in the art, in conjunction with the asset-tracking application server, Class Based Networks facilitate automated and semi-automated segregation, tracking, monitoring, and delivery of assets. The server issues, via the Gateway, class-directed messages to monitor and track WRT Classes. User-defined class granularity facilitates the use of separate categories and/or subcategories for various attributes and states of the assets, e.g., production batches, phases of production, and the delivery process. By increasing granularity, i.e., using many categories or subcategories (including sub-subcategories and so on), messages or other class-directed communications from the application server can be directed to only those classes of interest representing such categories, subcategories, or sub-subcategories, as desired. Furthermore, because messages or other class-directed communications are transmitted in packets that specify class designations for intended transceiver recipients, only those transceivers that are members of the specified class awaken from standby mode to receive and process the packets, and then to acknowledge or reply thereto as appropriate. Accordingly, this reduces RF interference and power consumption otherwise experienced, while making asset-tracking functions more efficient.

[0111] Once established, the Class Based Networks provide functionality as a dynamic distributed hierarchical database system. In this regard, Wireless Reader Tags and Wireless Tags preferably include a handling routine in communication with a memory of the Wireless Reader Tags and Wireless Tags. The handling routine interprets and responds to class-directed database commands, e.g., data queries or data updates from an asset-tracking application or a Communicator. Database queries may include status queries that provide the asset-tracking application with real-time up-to-date status information about tagged assets. Data updates may include requests to change data maintained on specified Wireless Reader Tags of the distributed database system. Similar to network formation communications, class-directed database commands include preambles that identify a WRT Class of Wireless Reader Tags to which they are directed. In this manner, only those Wireless Reader Tags of the selected class need process the database command. Class-directed database commands may also include, in their preambles, a wildcard that indicates to query handling routines that all Wireless Reader Tags of a particular abstracted WRT Class should receive and process the database commands. Class-directed commands thereby avoid unnecessary radio interference and reduce power consumption by Wireless Reader Tags that are clearly outside the scope of the database search criteria. Database performance is also enhanced by selecting Wireless Reader Tag classes and class abstractions in a way that mirrors a preferred hierarchical structure for the data they contain. In this way, increased class granularity facilitates improved data retrieval efficiency in the distributed database system by reducing the number of Wireless Reader Tags that must be involved in a database query or update transaction. The Class Based Networks themselves act as a hierarchical database facilitating fast and efficient database queries.

[0112] The CBNF routine used to form the Class Based Networks in accordance with the present invention may also be used to perform autonomous modification and reconfiguration of such networks in response to changes in the location, status, behavior, characteristics or class designation of Wireless Reader Tags and/or Wireless Tags.

[0113] Similarly, the self-configuration methods of the present invention facilitate maintenance of radio communication links in response to changes in the operational characteristics of the Wireless Reader Tags and/or Wireless Tags that comprise the network fabric. For example, self-configuration routines are responsive to changes caused by battery drain, radio transmitter failures, radio interference, and digital processor failure, by their inherent methods of organizing the network to have optimal link integrity and node connectivity.

[0114] Functions/Commands

[0115] The following functions preferably are supported in an Wireless Reader Tag of the present invention-and in a Wireless Tag, where indicated-to accomplish the aforementioned class based network formation and subsequent reformation. The name of the function is followed by the description of the function in the context of the type of transceiver in which it is to be implemented, i.e., Wireless Reader Tag and/or Wireless Tag.

[0116] “Acquire Class or Sub-Class Structures”—Software on the Wireless Reader Tags and Wireless Tags interprets category and subcategory structures represented by WRT and WT Classes, respectively. To initialize, the Wireless Reader Tags arbitrarily form networks based on the ability to talk to other Wireless Reader Tags. When a Wireless Reader Tags wakes up it broadcasts a message to other Wireless Reader Tags that it is a primary unit seeking secondary units. Other Wireless Reader Tags awaken to receive the message and attempt to register with the primary unit. If they are unable to communicate with the primary unit, or if the primary unit's cluster is full, then the secondary units will attempt to become a primary unit and continue the process. Once Wireless Reader Tags have established a network, the highest primary unit of the hierarchy contacts the Gateway and communicates with the application server, whereupon a profile is downloaded to the primary unit and passed on to each Wireless Tag of the network. The profile downloaded is based on options such as reading Wireless Tags, WRT IDs, business rules located at the application server and other information that has been downloaded by a Communicator. For example, and with regard to a WRT, the profile is a list of attributes or “personalities” assigned to each WRT. The list in the profile will be determined by business rules (like “things move into the shipping are ready to be shipped”, “all fresh meat shipments must leave the plant within 24 hours of packing”, etc.); a Communicator (used, for example, by a supervisor who views the asset and determines that it needs another coat of painting and manually changes the class back to “pre-paint step”, etc.); and server application (first two-hundred assets shipped to New Jersey, next two-hundred assts shipped to Florida, last five-hundred assets shipped to California, etc.). The profile function can allow conditional class change.

[0117] Once the Wireless Reader Tags have their respective profiles, the Wireless Reader Tags reform in Class Based Networks based on rules defined by the software located on the Wireless Reader Tags. If readonly Wireless Tags are used, then the WR Class can be preprogrammed into the Wireless Tags but will not be able to be modified dynamically. The dynamic acquisition of a WRT Class is based on rules defined by the application server.

[0118] “Allow Class/State Change”—Class changes are allowed based on business rules setup by the customer to track and group their assets. The rules are built into the server application and the software on the Wireless Reader Tags. The profile provides information that allows dynamic decisions to be made by the Wireless Reader Tags. Once the Wireless Reader Tags have determined that their category, subcategory, etc. as represented by their WRT Class has changed, the Wireless Reader Tags must join the new WRT Class. The ability to allow such a class change provides functionality to allow dynamic changes to WRT Class by a Wireless Reader Tag. For example, with reference to FIGS. 10 and 10A, changing the WRT Class of the Wireless Reader Tag E to “/circle” from “/triangle” causes Wireless Reader Tag E it to join the Class Based Network for the circle, either as a secondary unit in a cluster of an existing primary unit (e.g., circle Wireless Reader Tag 5), or by becoming a primary unit itself. Continued contact between Wireless Reader Tag E and the WRT Class of triangles could be limited based on system rules, but preferably is terminated. In an example of this, the WRT class of triangles could represent goods in the process of being manufactured in a factory. When these goods enter a shipping section of the factory, the Wireless Reader Tags associated with the goods on the pallet would automatically acquire a “shipping” WRT Class representative of their current location and associated status in shipping.

[0119] “Form Class”—A Class Based Network for a new class can be established by downloading a new profile and using the command “Determine Primary”. The command then uses techniques in FIGS. 2-21 to establish the Class Based Network for the new class. Profiles and software on the Wireless Reader Tags form the basis for decisions on network formation. The profile must be preprogrammed in the Wireless Reader Tags or Wireless Tags or downloaded from the application server.

[0120] “Combine Classes”—The combination of classes is required when the user no longer wishes to differentiate between two originally defined classes. The profile is downloaded either as a new class profile that a new class name or downloads to the class to be replaced by the existing class. After combining classes, the Wireless Reader Tags may reform the network using the CBNF routines of the present invention.

[0121] “Determine Primary”—When a Wireless Reader Tag “wakes up”, it determines whether it is able to become a primary unit with the determine primary command. If the health of the device is sufficient, it sends out a message to other Wireless Reader Tags of its WRT Class for registration of secondary units.

[0122] “Ping MLG/Gateway/Communicator”—A Wireless Reader Tag incorporated into a MLG, Gateway, or Communicator sends out a special message identifying itself as part of an MLG, Gateway, or Communicator. The purpose of this message is to inform other Wireless Reader Tags in stand-alone mode that the Wireless Reader Tag incorporated into the MLG, Gateway, or communicator has additional capabilities. The identifying message allows the Communicator to query information from the Wireless Reader Tags or Wireless Tags while the message from the Gateway and MLG indicate an ability to communicate to the external network.

[0123] “Inventory WT Tags”—The Wireless Reader Tag will read all Wireless Tags within range. The profile downloaded from the application server will help the Wireless Reader Tag control misreads and extra tags.

[0124] Multiple reads of the tags insures high reliability.

[0125] “Report Communication Links”—Upon formation of a Class Based Network, a Wireless Reader Tag stores identifiers that describe the Wireless Reader Tags constituting neighbors in adjacent levels of the network hierarchy. The primary unit thus will store all the WRT IDs for its secondary units, while the secondary units will store the WRT IDs on the primary unit and any secondary units thereto. The knowledge of communication links, both upstream and downstream, supports responsiveness to queries from the application server.

[0126] “Report Local Classes”—By listening for preambles of data packets intended for other classes, Wireless Reader Tag may store WRT Class information about other Wireless Reader Tags in their vicinity. The Wireless Reader Tags will support queries from the application server to supply this intelligence regarding local class information, regardless of whether the reported class even maintains connectivity to the application server.

[0127] “Class Structure-Secondary only”—The secondary only command provides entry into a system without giving network formation rights. In this regard, the Wireless Reader Tag with this designation in the profile is allowed to act like the other secondary Wireless Reader Tags, but it is unable to take on the role of a primary unit and, thus, is itself restricted from further propagating the network. This allows the Wireless Reader Tag the ability to move from one WRT Class to another WRT Class without otherwise disturbing the hierarchy of each Class Based Network of which it becomes a part. A practical of this command enables a customer, who walks into a warehouse retailer, to read product names, costs, or locations in the store without interrupting or disturbing the resident asset-tracking application.

[0128] Server Assisted Network Formation

[0129] The CBNF routines described above with reference to FIGS. 3-11 and 12-21 involved peer-centric network formation, in which Wireless Reader Tags self-formed an ad hoc Class Based Network and then contacted an application server via a Gateway. In this peer-centric method, each Wireless Reader Tag contains software that is preprogrammed to interpret class information contained in the of messages being transmitted by other Wireless Reader Tags and then negotiate to be a primary unit. The Wireless Reader Tags use commands such as inventory Wireless Tags, determine primary, and others (described above) to make decisions on class and other profile information that has been preprogrammed in the Wireless Reader Tags. Once the Wireless Reader Tags have formed the Class Based Network, information is transmitted by the Wireless Reader Tags for connectivity to server applications.

[0130] Other network propagation methods within the scope of the present invention are contemplated, and include a server-initiated method and a client/server shared method. In the server-initiated method, the Wireless Reader Tags are attached to pallets or areas to read information from Wireless Tags. The Wireless Reader Tags are turned on and first form an arbitrary network using commands such as Determine Primary. This arbitrary formation is done so that the server can address particular Wireless Reader Tags, and the formation is not based on class designations. The Wireless Tags are read by the Wireless Reader Tags and profiles are downloaded to the Wireless Tags from the Wireless Reader Tags based on commands such as “Inventory RF Tags”, described above. Profiles defining a new class structure are then downloaded from the server to the Wireless Reader Tags (and any read/write Wireless Tags) based on business rules. The Wireless Reader Tags are then instructed to Determine Primary again, whereby Class Based Networks are formed according to the newly-assigned class structure. In this regard, the profiles are lists of options that the Wireless Reader Tag can use to make decisions. For example, if a pallet has TVs on it and the profile lists possible products as VCRs, TVs, Cameras and Unknown, then the Wireless Reader Tag knows to adopt the class of TVs and form a network accordingly. If TV was not in the list, then the Wireless Reader Tag could adopt the class Unknown and generate a system flag for further analysis.

[0131] In the client/server shared method, the Wireless Reader Tags are loaded with software preprogrammed to interpret profile information. The profile information may include WT IDs, states, and the like. The Wireless Reader Tags then are reset and boot up looking to read the saved profile, to form hierarchical networks based on class designations specified in the profile, and to look for primary/secondary configurations. Once the Wireless Reader Tags have setup the initial network, network server business rules are downloaded to the Wireless Reader Tags in the form of new profiles to “fine tune” the network. In this regard, general information about how a particular business operates is used to setup the network. Not enough information is known, however, about the assets. In this case, information can be stored in the Wireless Tags as they are attached to the assets, and profiles in the Wireless Reader Tags can enable the Wireless Reader Tags to read this information and make intelligent decisions about how to efficiently setup the network so that the data is an organized within the database in a performance-enhancing fashion.

[0132] The following are examples of asset-tracking applications within the scope of the present invention.

Example 1

[0133] Tagged Luggage System

[0134] When a passenger checks in at the airport a Wireless Tag is attached to each item of the passenger's luggage. A corresponding Wireless Tag identifying the passenger is provided to the passenger to verify his/her identity at the destination baggage pickup location. A Wireless Reader Tag near the check-in counter detects and logs the Wireless Tags for the luggage in association with the passenger's Wireless Tag and related information into the asset-tracking system. The asset-tracking system downloads a profile into each of the Wireless Tags as identified by the Wireless Reader Tag at the check-in counter. The profiles are in the format:

[0135] :Tag_Type:Airline_Name:Passenger_Class:Origin_and_Destination:Flight

[0136] An example of the profile for the passenger's Wireless Tag is:

[0137] passenger: Delta_Airlines:First_Class:ATL-SEA:FLT-490:check-in:45567788KDKO8

[0138] while an example of the profile for the luggage Wireless Tag is:

[0139] :baggage:Delta_Airlines:FirstClass:ATL-SEA:FLT-490:check-in:45567788KDKO8

[0140] Upon successful check-in, the luggage is placed on the conveyer belt where it is read by another Wireless Reader Tag. By way of a communication from the Wireless Reader Tag, the profile of each Wireless Tag on the luggage then is modified by altering the Tag_Status field from “check-in” to “luggage-transfer_station_4334,” which identifies a location of the Wireless Reader Tag at the conveyor belt. Multiple Wireless Reader Tags are positioned along the conveyer belt system to identify the specific area of location of the luggage as it progresses. Trucks that deliver the luggage to the plane also have Wireless Reader Tags attached to the truck and alter the Tag_Status to “departure_on-transfer-truck-1441”. Once the luggage is placed on the plane, yet another Wireless Reader Tag detects and logs the Wireless Tag into the asset-tracking system, whereupon a cross-check is made of the luggage as identified by the WT IDs with the luggage that is supposed to be on the plane. Any luggage that is not supposed to be on the plane is flagged for removal by the asset-tracking system and rerouted to its proper destination. Any luggage that is not accounted for raises an alarm, so that attendants are alerted to its arrival time, its position, or its last known position and an investigation can be made.

[0141] Once the plane arrives at its destination, the Wireless Tags of the luggage are detected and logged in by an Wireless Reader Tag and the Tag_Status field of each Wireless Tag is changed to “arrival_on-transfer-truck-6633”. At the destination baggage pickup, the Wireless Tags on the luggage are read by a Wireless Reader Tag located near an exit of the baggage area. The Wireless Reader Tag detects and logs the luggage Wireless Tags in association with the Wireless Tag of the passenger claiming the luggage, whereupon the asset-tracking system assures that the passenger claiming the luggage is authorized to do so. A passenger inadvertently selecting the wrong luggage may then be alerted to the error.

Example 2

[0142] Warehouse/Retail System

[0143] A warehouse store such as Costco carries hundreds of brands of products. Nevertheless, all products need to be inventoried on a realtime basis. In accordance with the present invention, a Wireless Reader Tag is attached to each pallet of goods and assigned a class designation that denotes the manufacturer of goods on that pallet (e.g., Pillsbury, Sony, Kellogg's, etc.). Each Wireless Reader Tag may also include in its class designation or profile, information about the goods on the pallet. Each boxes on the pallet carries a Wireless Tag that is read by the Wireless Reader Tag of the pallet. On demand, each Wireless Reader Tag gathers information about the Wireless Tags on its pallet and relays the information back to the asset-tracking application server. At any given time, an employee of the warehouse store can inventory goods of a selected manufacturer by sending a query that will be received only by Wireless Reader Tags of the selected class corresponding to such manufacturer. Messages directed to a selected class will not appreciably affect the battery life of Wireless Reader Tags of other classes, as only Wireless Reader Tags of the selected class will wake up from standby mode to receive the messages and process the query. The manufacturer classes can be divided further into categories and subcategories, thereby further collectively reduce battery consumption and radio interference.

Example 3

[0144] Shipping Containers Tracking System

[0145] Containers full of material shipped via rail or ship can be received and logged into a yard by manufacture based on class information stored on Wireless Reader Tags. The Wireless Reader Tags form a network with other containers from a particular manufacturer and allow quick and efficient tracking of containers. Messages directed to a selected class will not affect the battery life of Wireless Reader Tags of other classes because only Wireless Reader Tags of the selected class will wake up from standby to receive the messages and process the queries. The manufacturer classes can be divided into categories and subcategories, thereby further collectively reduce battery consumption and radio interference.

Example 4

[0146] Manufacturing and Supply Chain Tracking System

[0147] A computer manufacturer may track the status of its supply chain in accordance with the asset-tracking application of the present invention. The classes defined are “raw material,” “component stuffing,” “monitor assembly,” “final assembly,” “shipping,” “in transit,” and “distributor.” The manufacture can inventory raw material throughout the process by addressing the raw material class, and can find out where in the manufacturing process the computer has reached by addressing monitor assembly or final assembly classes.

[0148] In view of the foregoing detailed description of preferred embodiments of the present invention, it readily will be understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. While various aspects have been described in the context of arborist uses, the aspects may be useful in other contexts as well. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications, and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. Furthermore, any sequence(s) and/or temporal order of steps of various processes described and claimed herein are those considered to be the best mode contemplated for carrying out the present invention. It should also be understood that, although steps of various processes may be shown and described as being in a preferred sequence or temporal order, the steps of any such processes are not limited to being carried out in any particular sequence or order, absent a specific indication of such to achieve a particular intended result. In most cases, the steps of such processes may be carried out in various different sequences and orders, while still falling within the scope of the present inventions. Accordingly, while the present invention has been described herein in detail in relation to preferred embodiments, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended nor is to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof.

[0149] For example, those skilled in the art now also will recognize that methods of network formation other than the described top-down and bottom-up processes may be used to propagate a Class Based Network based on a multi-level hierarchy by the Wireless Reader Tags. For example, a middle-outward approach or star configuration may be used to propagate the hierarchical network.

[0150] Also, for purposes of describing preferred embodiments of the present invention, it has been assumed herein that each WRT Class has more than one member. Otherwise, the sole member of the WRT Class communicates directly with a Gateway. However, this scenario is contemplated within the scope of the present invention.

[0151] Furthermore, while each Wireless Reader Tag has been described as belonging to a particular WRT Class, class membership for each Wireless Reader Tag need not necessarily be exclusive, and a Wireless Reader Tag therefore may belong to more than one WRT Class as desired in any particular application of the present invention. Moreover, while each WRT Class has been described as reading a particular WT Class associated therewith, each Wireless Reader Tag may read Wireless Tags associated with different WRT Classes, as desired in the asset-tracking application.

[0152] With regard to the distinction between Wireless Reader Tags and Wireless Tags, it is noted that each Wireless Reader Tag includes the capabilities of each Wireless Tag and, therefore, it is contemplated within the scope of the present invention that each Wireless Tag of the present invention could be replaced with a Wireless Reader Tag.

[0153] Finally, if a Wireless Tag is passive, which is contemplated within the scope of the present invention, then it is believed that the Wireless Tag currently maintains therein only its unique WT ID. Being passive, no other information is maintained in the Wireless Tag. In this case, an associated Wireless Reader Tag maintains the identification of its WT Class in memory as indexed by the respective WT ID of the passive Wireless Tag. Any other information, if maintained, also is stored in the Wireless Reader Tag and indexed by WT ID, where appropriate. Of course, in this scenario, any broadcast generally is answered by each passive Wireless Tag that is within broadcast range and, hence, such implementation of passive Wireless Tags, while within the scope of the present invention, is not preferred. 

1. A method of forming a wireless data communication network among transceivers, each transceiver including a designation with a first plurality of transceivers having a first common designation and a second plurality of transceivers having a second common designation different from the first common designation, the method comprising the steps of: (a) forming an ad hoc hierarchical network for each of the first plurality and second plurality of transceivers; and (b) communicating to an external network from each transceiver of each ad hoc hierarchical network by, (i) establishing a communication link between each transceiver in a level of the ad hoc hierarchical network, other than the highest level, with a transceiver in the next higher level of the ad hoc hierarchical network such that transceivers pass communications upward in the ad hoc hierarchical network; and (ii) establishing a communication link between a transceiver in the highest level of the ad hoc hierarchical network and an external network access transceiver, such that communications from transceivers in the ad hoc hierarchical network are passed through the transceiver in the highest level of the ad hoc hierarchical network to the external network access transceiver.
 2. A method of forming a wireless data communication network among transceivers in an asset-tracking system, each transceiver including a class designation with a first plurality of transceivers having a first class designation and a second plurality of transceivers having a second class designation different from the first class designation, the method comprising the steps of: (a) forming an ad hoc hierarchical class based network for each of the first plurality and second plurality of transceivers; and (b) communicating to an external network from each transceiver of each ad hoc hierarchical class based network by, (i) establishing a communication link between each transceiver in a level of the ad hoc hierarchical class based network, other than the highest level, with a transceiver in the next higher level of the ad hoc hierarchical class based network such that transceivers pass communications upward in the ad hoc hierarchical class based network; and (ii) establishing a communication link between a transceiver in the highest level of the ad hoc hierarchical class based network and an external network access transceiver, such that communications from transceivers in the ad hoc hierarchical class based network are passed through the transceiver in the highest level of the ad hoc hierarchical class based network to the external network access transceiver.
 3. The method of claim 2, wherein said step of forming an ad hoc hierarchical class based network for each of the first plurality and second plurality of transceivers comprises the steps of: (a) filtering, by each transceiver, transmissions from other transceivers for an identification of its class designation within the transmission; (b) transmitting, from a primary transceiver of the first plurality, a primary availability signal including an identification of the first class designation and an identification of the primary transceiver transmitting the primary availability signal; (c) transmitting, from a primary transceiver of the second plurality, a primary availability signal including an identification of the second class designation and an identification of the primary transceiver of the second plurality transmitting the primary availability signal; (d) transmitting, from a transceiver receiving a primary availability signal having an identification therein of its class designation, a registration signal including an identification of the class designation and an identification of the transceiver transmitting the registration signal; (e) identifying a transceiver transmitting a registration signal as a secondary transceiver by a primary transceiver of the same class designation, the primary transceiver thereby assuming a higher level in the ad hoc hierarchical class based network relative to the said identified secondary transceiver such that communication from the secondary transceiver to the external network is passed to the primary transceiver.
 4. The method of claim 3, further comprising the step of identifying a transceiver transmitting a registration signal as a newly promoted primary transceiver by a primary transceiver of the same class designation when the communication channel capacity of the primary transceiver is reached, the primary transceiver thereby assuming a lower level in the ad hoc hierarchical class based network relative to the said identified newly promoted primary transceiver such that communication from the primary transceiver to the external network is passed to the newly promoted primary transceiver and such that communication to the external network from any secondary receivers of the primary transceiver is passed through the primary transceiver to the newly promoted primary transceiver.
 5. The method of claim 4, wherein said step of forming an ad hoc hierarchical class based network comprises forming a ad hoc hierarchical class based network in a bottom-up manner.
 6. The method of claim 3, further comprising the step of identifying, by a primary transceiver when the communication channel capacity of the primary transceiver is reached, a secondary transceiver thereof as a new primary transceiver of the next lower level of the ad hoc hierarchical class based network, the new primary transceiver then transmitting a primary availability signal including an identification of its class designation and an identification of itself for identifying secondary receivers relative thereto, whereby communication to the external network from any secondary transceivers relative to the new primary transceiver is passed to new primary transceiver and then passed to the primary transceiver in the next higher level of the ad hoc hierarchical class based network.
 7. The method of claim 6, wherein said step of forming an ad hoc hierarchical class based network comprises forming a ad hoc hierarchical class based network in a top-down manner.
 8. The method of claim 2, wherein the primary transceivers of the highest levels of the ad hoc hierarchical class based networks are located within a broadcast area of the external network access transceiver.
 9. The method of claim 8, wherein other transceivers of the ad hoc hierarchical class based networks are not located within a broadcast area of the external network access transceiver.
 10. The method of claim 2, wherein a communication from the external network is broadcast by the external network access transceiver to all transceivers within the broadcast area of the external network access transceiver.
 11. The method of claim 10, wherein the communication includes an identification of a class designation and only those transceivers having a matching class designation receive and process the communication from the external network access transceiver.
 12. The method of claim 2, wherein a communication from the external network is broadcast by the external network access transceiver to a transceiver in the highest level of each ad hoc hierarchical class based network and not to all transceivers within the broadcast area of the external network access transceiver.
 13. The method of claim 12 wherein each transceiver in the highest level of each ad hoc hierarchical class based network retransmits the communication from the external network access transceiver to other transceivers in its ad hoc hierarchical class based network.
 14. The method of claim 12 wherein the external network access transceiver transmits the communication at a reduced power level.
 15. The method of claim 12 wherein the external network access transceiver transmits the broadcast at a reduced power level.
 16. The method of claim 12 wherein the transceivers in the highest level of the ad hoc hierarchical class based networks represent the physically closest transceiver to the external network access transceiver for its respective class designation.
 17. The method of claim 12, wherein the communication includes an identification of transceivers in the highest level of the ad hoc hierarchical class based networks.
 18. The method of claim 2, wherein the transceivers are used to track assets.
 19. The method of claim 18, wherein the transceivers of the first and second pluralities are used to communicate with the transceivers attached to the tracked assets.
 20. The method of claim 19, wherein the transceivers attached to the tracked assets comprise transponders.
 21. The method of claim 19, wherein the transceivers attached to the tracked assets are semi-passive and the each of the first plurality and second plurality of transceivers are active.
 22. The method of claim 19, further comprising the step of assigning a class designation to each plurality of transceivers based on a common characteristic or behavior of the assets associated with the transponders when read by each of the plurality of transceivers.
 23. An ad hoc class based network formed in accordance with the step of the method of claim
 2. 24. The wireless data communication network formed by the method of claim
 2. 25. The wireless data communication network of claim 24, wherein said wireless data communication network comprises a distributed hierarchical database for tracking assets.
 26. Computer readable-medium having computer-executable instructions for performing the ad hoc class based network formation steps recited in claim
 3. 27. A transceiver including the computer-readable medium recited in claim
 26. 28. A method for communicating to a recipient transceiver from a plurality of transceivers, the plurality of transceivers being located within the broadcast range of the recipient transceiver, the method comprising the steps of: (a) transmitting a communication at a first power level such that only a first group of transceivers receive the broadcast, the communication including a command causing each of the first group of transceivers not to respond to a subsequent broadcast; and subsequent thereto (b) transmitting a communication at a second power level greater than the first power level such that a second group of transceivers greater than and including the first group of transceivers receive the broadcast, but such that only a limited number of transceivers of the second group respond to the broadcast, the limited number of transceivers excluding the first group of transceivers.
 29. A method for communicating to a recipient transceiver from a plurality of transceivers, the plurality of transceivers being located within the broadcast range of the recipient transceiver and the plurality of transceivers exceeding the number of transceivers from which communications can be received by the transceiver without radio frequency interference due to its channel capacity, the method comprising the steps of: (a) transmitting a communication at a first power level such that only a first group of transceivers receive the broadcast, the first group in number of transceivers being not greater than the number of transceivers from which communications can be received by the transceiver without radio frequency interference due to its channel capacity, the communication including a command causing each of the first group of transceivers not to respond to a subsequent broadcast; and subsequent thereto (b) transmitting a communication at a second power level greater than the first power level such that a second group of transceivers greater than and including the first group of transceivers receive the broadcast, but such that only a limited number of transceivers of the second group respond to the broadcast, the limited number of transceivers excluding the first group of transceivers and comprising not greater the number of transceivers from which communications can be received by the transceiver without radio frequency interference due to its channel capacity.
 30. The method of claim 29, wherein the recipient transceiver comprises an external network access transceiver.
 31. The method of claim 29, wherein each of the plurality of transceivers comprises a transceiver attached to an asset to be tracked.
 32. The method of claim 31, wherein the transceivers attached to the tracked assets comprise transponders.
 33. The method of claim 31, wherein the transceivers attached to the tracked assets are semi-passive and the recipient transceiver is active.
 34. The method of claim 29, wherein each of a first set of transceivers of the plurality of transceivers includes a first class designation and each of a second set of transceivers of the plurality of transceivers includes a second class designation different from the first class designation, and wherein each communication includes an identification of one of the class designations.
 35. The method of claim 34, further comprising the step of assigning a class designation to each of the plurality of transceivers.
 36. The method of claim 34, further comprising the step of filtering, by each transceiver of the plurality, communications from the recipient transceiver for an identification of its class designation within the communication.
 37. The method of claim 36, further comprising ignoring, by each transceiver of the plurality, each communication if an identification of its class designation is not found therein.
 38. The method of claim 34, wherein each of the plurality of transceivers comprises a transceiver attached to an asset to be tracked.
 39. The method of claim 38, wherein each class designation of the transceivers represents a common characteristic or behavior of the asset tracked thereby. 